Various equipments for protecting an audio apparatus for a vehicle from theft have been proposed since such apparatuses are often stolen.
Among the various equipments proposed are security equipment for which a user can easily release a security operation even while the audio apparatus is executing the security operation without decreasing security performance. A security equipment making use of TOC (TABLE OF CONTENTS) information of a compact disc (hereinafter referred to as "CD") and the like is proposed in Japanese patent application PH5-327672 (Published Unexamined Patent Application (Kokai) PH7-182840).
The security equipment making use of the TOC information is explained below.
The TOC information is information recorded on a read in area of a CD and the like. As shown in FIG. 5, the CD comprises a read in area 31, a data area 32, a read out area 33. The TOC information is recorded on a read in area 31, and it contains characteristic data (the number of music tracks, the start of music data, and the playing time) of the disk.
In order to set the security mode of the audio apparatus, TOC information of the prescribed CD is previously written into a memory of the audio apparatus, for example, an electrically erasable programmable ROM (EEPROM) and the like.
If the audio apparatus is stolen from the vehicle under the condition that the security mode is set, the security operation is executed as follows. When the audio apparatus is stolen from the vehicle, the audio apparatus is disconnected from the vehicle battery. The security equipment detects this change of connecting condition with the battery by a change of power source and stores it. When the audio apparatus is fitted to another vehicle and connected again to a battery, the security equipment executes the security operation because the fact that the battery has been once disconnected is stored. If the security operation is executed, the audio apparatus becomes inoperable and does not accept switching operation, etc. except when a special operation is executed.
Therefore, if a person other than the user takes the audio apparatus away from the vehicle, the person cannot use the apparatus. By displaying on the vehicle or on the apparatus that such a security function is provided, it reduces the likelihood of theft.
However, if the security mode is set, it may occur that the audio apparatus becomes inoperable even while a user uses the audio apparatus properly, because the security operation may be triggered by the discharge of the vehicle battery and the like.
In order to reset the inoperable condition, the user inserts the CD used for setting up the security mode or an identical CD into the CD player of the audio apparatus. The security equipment reads in the TOC information from the inserted CD, and if it is identical to the TOC information recorded in the memory, the security equipment resets the inoperable condition and the audio apparatus can be used as usual.
On the other hand, even though a person who stole the audio apparatus connects the audio apparatus to a battery and tries to operate it, it cannot be used since it is in an inoperable condition as described above. For example, even if a CD is inserted into the CD player, the chance that the inserted CD is identical to the CD which was used to set up the security mode is very small. Thus if any other CD is inserted, the TOC information of the inserted CD is not identical with the TOC information in the memory. Therefore, the release of the security operation is not executed and the audio apparatus is kept inoperable.
When the insertion of a CD, which is not the prescribed CD, is repeated more than a defined number of times (i.e., five times or ten times), the inoperable condition cannot be released, and thus raises the reliability of the security.
If the user forgets or loses the CD which was used for setting the security mode, the security mode can be released according to the proper process of carrying it in to a dealer or the like.